Single-crystal electronic and electron spin resonance spectra of the square pyramidal µ-formato-mono(diethylenetriamine)copper(II) formate

Abstract

The polarised single-crystal eletronic spectra, e.s.r. spectra, and bulk magnetic susceptibility of µ-formato-mono-(diethylenetriamine) copper(II) formate have been measured. The correlation of the single-crystal g-values and the crystallographic data suggests a d_x²–y² ground-state for the approximately square-pyramidal CuN₃O₂ chromophore. The room-temperature magnetic moment of 1·95 BM and a Weiss constant of θ=–5° suggest negligible antiferromagnetism. The polarised single-crystal electronic spectra are interpreted in C_2v effective symmetry and yield a tentative one-electron orbital sequence d_x³–y² > d_z² > d_xy > d_xz > d_yz. The energies of these transitions are compared with those of the corresponding transitions of other copper(II) complexes having a square-pyramidal stereochemistry.